Preparation of linear, basic polymer powders

Abstract

Linear, basic polymer powders which contain units of the formula <IMAGE> (I) and have a Fikentscher K value of from 10 to 200 are prepared by eliminating the formyl groups from N-vinylformamide polymer powders with a gaseous hydrogen halide in the presence of not more than 5% by weight, based on the polymer used, of water.

We claim: 
     
       1. A process for the preparation of a linear, basic polymer powder which contains units of the formula ##STR7## and has a Fikentscher K value of from 10 to 250 (measured at a polymer concentration of 0.5% by weight in 5% strength aqueous sodium chloride solution at 25° C., wherein the formyl groups are eliminated from an N-vinylformamide polymer powder which contains no more than 5% by weight of water by reaction with a gaseous hydrogen halide at up to 200° C., with formation of units of the formula I. 
     
     
       2. A process as claimed in claim 1, wherein the reaction is carried out using gaseous hydrogen chloride or hydrogen bromide in the presence of not more than 2.5% by weight of water. 
     
     
       3. A process as claimed in claim 1, wherein the reaction is carried out in the absence of water. 
     
     
       4. A process as claimed in claim 1, wherein the reaction is carried out in the presence of an inert suspending agent which does not dissolve the polymer particles. 
     
     
       5. A process as claimed in claim 4, wherein the suspending agent used is dioxane, tetrahydrofuran or cyclohexane. 
     
     
       6. A process as claimed in claim 1, wherein elimination of the formyl groups is carried out in a C 1-  C 8  -alcohol. 
     
     
       7. A process as claimed in claim 6, wherein an inert suspending agent is used in addition. 
     
     
       8. A process as claimed in claim 1, wherein the particle size of the N-vinylformamide polymer is from 10 to 1000 μm. 
     
     
       9. A process as claimed in claim 1, wherein the particle size of the N-vinylformamide polymer is from 50 to 400 μm. 
     
     
       10. A process as claimed in claim 1, wherein the reaction is carried out at from 35° to 150° C.